Method and apparatus for providing a centralized subscriber load distribution

ABSTRACT

A method and apparatus for providing subscriber load distribution in networks are disclosed. For example, the method receives capacity data and user equipment (UE) resource consumption data from a plurality of devices that process call control signaling messages within the communication network. The method receives a first request from one of the plurality of devices to re-register one or more selected user equipment, and selects at least one available device from the plurality of devices. The method then re-registers the one or more selected user equipment on the at least one available device.

This application is a continuation of U.S. patent application Ser. No.13/687,799, filed Nov. 28, 2012, now U.S. Pat. No. 9,071,527, which is acontinuation of U.S. patent application Ser. No. 12/014,489, filed Jan.15, 2008, now U.S. Pat. No. 8,339,956, all of which are hereinincorporated by reference in their entirety.

The present invention relates generally to communication networks and,more particularly, to a method and apparatus for providing subscriberload distribution from a centralized location in networks, e.g., packetnetworks, Internet Protocol (IP) networks, Voice over Internet Protocol(VoIP) networks, IP Multimedia Subsystem (IMS) networks, Virtual PrivateNetworks (VPN), etc.

BACKGROUND OF THE INVENTION

When a customer wishes to access a network service, e.g., a Voice overInternet Protocol (VoIP) service, the customer's User Equipment (UE) isregistered with a host server, e.g., a server with a Serving-CallSession Control Function (S-CSCF). Current methods distribute UEs acrossmultiple servers with an S-CSCF function at registration time with noregard to the offered load. A UE may be re-registered on another S-CSCFserver only under an exceptional condition, such as a network elementfailure. As such, call volumes may not be balanced across multipleS-CSCF servers.

SUMMARY OF THE INVENTION

In one embodiment, the present invention discloses a method andapparatus for providing subscriber load distribution from a centralizedlocation within a network. For example, the method receives capacitydata and user equipment (UE) resource consumption data from a pluralityof devices that process call control signaling messages within thecommunication network. The method receives a first request from one ofthe plurality of devices to re-register one or more selected userequipment, and selects at least one available device from the pluralityof devices. The method then re-registers the one or more selected userequipment on the at least one available device.

In one alternate embodiment, the method measures a resource capacity ofa device that processes call control signaling messages within thecommunication network, and measures a peak period volume for each of aplurality of registered user equipment that is registered with thedevice. The method determines whether a peak period volume of the deviceexceeds or reaches an on-set threshold of the device. The method selectsone or more of the plurality of registered user equipment if the on-setthreshold of the device is reached or exceeded, where a sum of the peakperiod volumes of the selected one or more plurality of registered userequipment is larger than or equal to a volume of traffic that is inexcess of the on-set threshold, or in excess of an off-set threshold ofsaid device. The method sends a request for the selected one or moreplurality of registered user equipment to be re-registered to anotherdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary network related to the presentinvention;

FIG. 2 illustrates an exemplary network with the current invention forproviding subscriber load distribution;

FIG. 3 illustrates a flowchart of a method for providing a subscriberload distribution; and

FIG. 4 illustrates a flowchart of a method for providing a subscriberload distribution; and

FIG. 5 illustrates a high-level block diagram of a general-purposecomputer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present invention broadly discloses a method and apparatus forproviding centralized subscriber load distribution within a network.Although the present invention is discussed below in the context ofpacket networks, e.g., Internet Protocol (IP) networks, the presentinvention is not so limited. Namely, the present invention can beapplied to other packet networks and the like.

FIG. 1 is a block diagram depicting an exemplary packet network 100related to the current invention. Exemplary packet networks includeInternet protocol (IP) networks, Ethernet networks, and the like. An IPnetwork is broadly defined as a network that uses Internet Protocol suchas IPv4 or IPv6 and the like to exchange data packets.

In one embodiment, the packet network may comprise a plurality ofendpoint devices 102-104 configured for communication with the corepacket network 110 (e.g., an IP based core backbone network supported bya service provider) via an access network 101. Similarly, a plurality ofendpoint devices 105-107 are configured for communication with the corepacket network 110 via an access network 108. The network elements 109and 111 may serve as gateway servers or edge routers for the network110.

In one embodiment, a registrar 150 is illustrated in network 110. Theregistrar 150 broadly encompasses a Serving-Call Session ControlFunction (S-CSCF), e.g., as implemented on a server. It should be notedthat a plurality of registrars (not shown) can be deployed in thenetwork 110. In operation, a user endpoint will be registered to oneregistrar among a plurality of registrars within network 110.

The endpoint devices 102-107 may comprise customer endpoint devices suchas personal computers, laptop computers, Personal Digital Assistants(PDAs), servers, routers, and the like. The access networks 101 and 108serve as a means to establish a connection between the endpoint devices102-107 and the NEs 109 and 111 of the IP/MPLS core network 110. Theaccess networks 101 and 108 may each comprise a Digital Subscriber Line(DSL) network, a broadband cable access network, a Local Area Network(LAN), a Wireless Access Network (WAN), a 3^(rd) party network, and thelike. The access networks 101 and 108 may be either directly connectedto NEs 109 and 111 of the IP/MPLS core network 110, or indirectlythrough another network.

Some NEs (e.g., NEs 109 and 111) reside at the edge of the coreinfrastructure and interface with customer endpoints over various typesof access networks. An NE that resides at the edge of a coreinfrastructure is typically implemented as an edge router, a mediagateway, a border element, a firewall, a switch, and the like. An NE mayalso reside within the network (e.g., NEs 118-120) and may be used as amail server, honeypot, a router, or like device. The IP/MPLS corenetwork 110 also comprises an application server 112 that contains adatabase 115. The application server 112 may comprise any server orcomputer that is well known in the art, and the database 115 may be anytype of electronic collection of data that is also well known in theart. Those skilled in the art will realize that although only sixendpoint devices, two access networks, five routers, one registrar andso on are depicted in FIG. 1, the communication system 100 may beexpanded by including additional endpoint devices, access networks,border elements, routers, registrars, etc. without altering the presentinvention.

The above IP network is described to provide an illustrative environmentin which packets for voice and data services are transmitted onnetworks. When a UE registers with a registrar, e.g., a Serving-CallSession Control Function (S-CSCF), the amount of load to be produced bythe UE is often unknown. The registration is performed independent ofthe load that will be produced. As such, call volumes may not bebalanced across multiple S-CSCF functions and may contribute to S-CSCFoverload. When an S-CSCF is overloaded, calls are dropped, therebyresulting in customer dissatisfaction with the subscribed service andloss of revenue for the service provider.

For example, a UE may be an Internet Protocol—Private Branch Exchange(IP-PBX) servicing a call center that handles calls terminating to atoll-free number. The capacity of the server providing the S-CSCFfunction to the UE may limit the throughput of the UE. As a result, theIP-PBX servicing the toll-free number may have a capacity need thatcannot be sufficiently met by the S-CSCF server with whom the IP-PBX hasregistered with during an initial registration process.

In one embodiment, the current method provides a centralized loaddistribution method or algorithm that enables a load managing server,e.g., a Home Subscriber Server (HSS), to periodically redistributeregistered UEs to different S-CSCFs. To better understand the currentinvention, the following networking terminology will first be provided:

a) Home Subscriber Server (HSS); and

b) Serving-Call Session Control Function (S-CSCF).

Home Subscriber Server (HSS) refers to a server with a database forstoring user data, e.g., registration status, the S-CSCF that serves theuser, the service profile associated with the user, etc., required by acore network to fulfill its duties. The HSS also performs authenticationand authorization of the user and may provide information about thelocation of the user.

Serving-Call Session Control Function (S-CSCF) is the central node ofthe signaling plane for performing session control and the SIP registrarfunction binding the UE to the S-CSCF. Broadly defined, an S-CSCFprocesses call control signaling messages. In one embodiment, it can beimplemented as a registrar or a Session Initiation Protocol (SIP)server. For example, the S-CSCF is located in the network and interfaceswith the HSS to download and upload user profiles. In one embodiment,the S-CSCF has no local storage of the user data. All necessaryinformation is loaded from the HSS. The S-CSCF sits on the path of allsignaling messages, and can inspect every message to decide to whichapplication server(s), if applicable, and to which next server a SIPmessage is to be forwarded.

FIG. 2 illustrates an exemplary network 200 of the current invention forproviding centralized subscriber load distribution. User Equipment (UEs)102-104 are accessing services from IP/MPLS core network 110. The UEsare in communication with a load managing server, e.g., a HSS 201 via aplurality of S-CSCFs 220-223 for registering and accessing services. TheHSS 201 selects one of the S-CSCFs 220-223 for each UE and enables theUEs to register with one of the assigned S-CSCFs 220-223. For example,UE 102 may be registered on S-CSCF 220, while UE 103 is registered onS-CSCF 221 and so on. Furthermore, each UE (e.g., UE 104) may have thecapability to communicate with more than one S-CSCF. Again, it should benoted that the number of UEs, S-CSCFs, and HSS shown in FIG. 2 is onlyillustrative and should not be interpreted as a limitation of thepresent invention.

In one embodiment, the current invention enables each S-CSCF server toperiodically measure its own S-CSCF resource capacity. The S-CSCF alsomeasures resource consumption for each registered UE. For example, anS-CSCF may measure a peak period volume for each registered UE. Forexample, an S-CSCF server may determine the peak volume for eachregistered UE on an hourly basis. It should be noted that the peakvolume can be measured in accordance with other predefined time periodsbased on the requirements of a particular implementation.

The S-CSCF then reports its own S-CSCF resource capacity and optionallyeach registered UE's resource consumption, e.g., peak period volumes, tothe HSS. The HSS may then track the availabilities and the peak periodvolumes (described below) of the S-CSCF servers. For example, the HSSmay receive the resource capacity and optionally UE's resourceconsumption data from each S-CSCF on an hourly basis. Thus, the HSS isprovided with the capability to track each S-CSCF's capacity and peakperiod volume over time.

In one embodiment, the service provider determines the peak periodlength for tracking the capacity of S-CSCF servers and/or tracking ofthe resource consumption by the UEs. The appropriate period of timedepends upon the type of service. For example, for uniform services withPoisson centralized arrivals, 1-hour may be used. For services withbursty arrivals, a shorter period of time such as 5 minutes may beneeded. For example, teleconferencing services may be grouped at fixedtime periods and may have arrival times that are bursty.

In one embodiment, the S-CSCF is able to detect when its peak periodvolume is exceeded in accordance with a pre-defined threshold. An S-CSCFmay have one or more thresholds for triggering load re-distribution,e.g., an on-set threshold, an off-set threshold, an overload threshold,a maximum capacity threshold, etc.

In one embodiment, the maximum capacity refers to an S-CSCF's capacitybeyond which the S-CSCF will no longer be able to process an additionaltransaction, and in fact, may start a maximum capacity method oralgorithm, e.g., selectively dropping packets, dropping set-up messages,and the like. An overload threshold for an S-CSCF refers to a thresholdthat is set to activate an overload method or algorithm so as to preventthe S-CSCF from reaching or exceeding its maximum capacity. For example,the overload method may activate various remedial steps, e.g.,triggering a warning message to a customer or to the service provider,requesting additional resources, requesting re-direction of traffic, andthe like.

In one embodiment, an on-set threshold for an S-CSCF refers to athreshold used to decide when a load balancing method or algorithm is tobe invoked. In contrast, an S-CSCF also has an off-set threshold used toterminate a redistribution of load process, i.e., to terminate the loadbalancing algorithm. The use of the on-set threshold in conjunction withthe off-set threshold will reduce oscillations where UEs are constantlybeing re-registered with different S-CSCFs. For example, the on-setthreshold is set to a larger value than the off-set threshold, but boththresholds are set below the overload threshold. As such, when a loadbalancing method is triggered after exceeding the on-set threshold, theload balancing method will continue to be in effect until the off-setthreshold is reached. Namely, the load balancing method will notterminate when the measured traffic volume falls below the on-setthreshold. Thus, the load balancing method will be triggered before theoverload threshold of the S-CSCF is reached.

It should be noted that the various thresholds can be set based upon apercentage of the maximum capacity of an S-CSCF. For example, anoverload threshold can be set at 90% of the maximum capacity. Similarly,an on-set threshold can be set at 80% of the maximum capacity and anoff-set threshold can be set at 70% of the maximum capacity. It shouldbe noted that the values set for these various thresholds can beselectively set by a service provider depending on the requirements of aparticular application or through the collection of statistics over aperiod of time.

In one embodiment, a particular S-CSCF may have detected that a peakperiod volume may have exceeded its on-set threshold. As part of theload balancing method, the S-CSCF may select one or more UEs whosecumulative peak period volume is larger than or equal to the volume oftraffic in excess of the on-set threshold. It should be noted that forsome network scenarios, selecting candidate UEs for a move to otherS-CSCFs based on consumption may not be practical. For example, a UE fora customer may be selected repeatedly for re-registration to otherS-CSCFs. In one embodiment, the frequency of moving the same UEs fromone S-CSCF to another may be reduced by using a random selectionmechanism. For example, the current method may use a random selectionalgorithm to select candidate UEs for load redistribution.

For example, the method may randomly select a list of candidate UEs thathas been reported by an S-CSCF. The method may then sum the peak periodvolumes of the selected UEs. If the sum of the peak period volumes ofthe selected UEs is less than the volume of traffic in excess of theon-set threshold (or alternatively the off-set threshold), then themethod adds more candidate UEs. The process continues until the sum isgreater than or equal to the traffic in excess of the on-set threshold(or alternatively the off-set threshold).

Then, the S-CSCF sends the list of the one of more randomly selected UEsand their respective resource consumption to the HSS. For example, thelist may contain randomly selected UEs, where the de-registration of oneor more of the listed UEs would result in the S-CSCF's peak periodvolume falling below its on-set threshold.

For each selected UE, the HSS then selects an available S-CSCF whosepeak period volume plus that of the UE is less than or below the off-setthreshold volume for said S-CSCF. For example, for each selectedregistered UE, the method may randomly identify a new S-CSCF amongS-CSCFs whose off-set threshold would not be exceeded after registeringthis new UE. For example, there may be 10 S-CSCFs with availablecapacity but there may be only one S-CSCF that will not exceed itsoff-set threshold after registering the selected UE. Then, the HSS willchoose the only S-CSCF that meets the criteria of not having its off-setthreshold exceeded.

Alternatively, the HSS may select an available S-CSCF whose peak periodvolume plus that of the UE is less than or below the on-set thresholdvolume for the S-CSCF instead of the off-set threshold volume for theS-CSCF. Namely, if the number of available S-CSCFs is limited, thenusing the off-set threshold may be too stringent. In another embodiment,a 2 phase approach can be implemented, e.g., first selecting an S-CSCFsuch that the cumulative peak volume plus that of the UE is less than orbelow the off-set threshold of the selected S-CSCF, but if such S-CSCFis not found, then selecting an S-CSCF such that the cumulative peakvolume plus that of the UE is less than or below the on-set threshold.

The HSS then re-registers or causes each of the selected one or more UEsto be re-registered to the selected S-CSCF. Those skilled in the artwill realize that the re-registering process of the selected UE onto anew S-CSCF implies a de-registration process from the previous S-CSCFhas occurred.

In one embodiment, the HSS re-registers a UE when the session is idle.For example, the HSS waits until the termination of the establishedsessions before performing de-registration of the UE with the currentS-CSCF and re-registration with the new S-CSCF. In one embodiment, theHSS subscribes to the S-CSCF to be notified when the UE is idle. Forexample, if an HSS receives a request from a first S-CSCF to move arandomly selected UE to another S-CSCF, then the HSS will subscribe withthe first S-CSCF to be notified when the selected UE is idle. The HSS isthen able to determine when the UE has no active sessions and to performthe re-registration without any service impact to the selected UE.

Alternatively, the HSS may re-register a UE only after a pre-provisionedperiod of time, e.g., based on average call hold time of the UE asmonitored by the S-CSCF, based on the time of day, based on a predefinedperiod of time, and so on.

In one alternate embodiment, re-registration may occur immediatelyregardless of whether or not there are one or more active sessions. Forexample, the reported volume for the UE is such that re-registrationshould be performed immediately to minimize service impact to thatparticular customer and/or to other customers serviced by the sameS-CSCF.

In one embodiment, the network service provider selectively determineswhen the re-registration is allowed, e.g., upon termination of activecalls, immediately or after a pre-determined time elapses. This allowsthe service provider the flexible control in dictating when and howre-registration will be implemented.

In one embodiment, the capacity data is sent to an HSS using a standardinformation exchange protocol, e.g., using a Diameter Watchdog Request(DWR) message. Thus, the present invention can be implemented using anexisting communication protocol.

FIG. 3 illustrates a flowchart of a method 300 for providing asubscriber load distribution. For example, method 300 can be implementedby a Home Subscriber Server (HSS). Method 300 starts in step 305 andproceeds to step 310.

In step 310, a Home Subscriber Server (HSS) receives capacity andoptionally UE resource consumption data from one or more S-CSCF serversin a pre-determined interval. For example, an HSS gathers peak periodvolumes and each registered UE's consumption data from a plurality ofS-CSCF servers, e.g., on an hourly basis.

In step 320, method 300 receives a request from an S-CSCF to re-registerone or more selected UEs. The said request includes the selected UEsrespective resource consumption. For example, a first S-CSCF serversends a request to the HSS to move a randomly selected list of UEs,e.g., to other S-CSCF servers such that its own peak period volume willreturn below its on-set threshold (or alternatively the off-setthreshold).

In step 330, method 300, the HSS, selects an available S-CSCF, for eachof the one or more selected UEs, whose peak period volume plus that ofthe selected UE's is less than (e.g., below) the off-set thresholdvolume for the available S-CSCF. For example, for each of said selectedregistered UE, the method may randomly identify a new S-CSCF amongavailable S-CSCFs whose off-set threshold would not be exceeded afterregistering the selected UE. Alternatively, the HSS, may select anavailable S-CSCF, for each of the one or more selected UEs, whose peakperiod volume plus that of the selected UE's is less than (e.g., below)the on-set threshold volume for the available S-CSCF.

In optional step 340, method 300 may request to be notified when aselected UE is idle. For example, the HSS may have received a requestfrom an S-CSCF to re-register a first UE. However, the UE may have oneor more active sessions. The HSS may then send a request to the currentS-CSCF to be notified when the first UE is idle.

In optional step 350, method 300 may receive a notification immediately,when a selected UE is idle, or after a preselected time period asdiscussed above. For example, the method may receive a response to therequest sent in step 340.

In step 360, method 300 re-registers one or more of the selected UEs onthe selected S-CSCF. It should be noted that more than one availableS-CSCF can be used to accept the re-registration of the selected UEs.The method then proceeds to step 370 to end processing the currentrequest or returns to step 310 and/or step 320.

FIG. 4 illustrates a flowchart of a method 400 for providing asubscriber load distribution. For example, method 400 can be implementedby an S-CSCF server. Method 400 starts in step 405 and proceeds to step410.

In step 410, method 400 measures resource capacity of an S-CSCF andmeasures resource consumption for each registered UE supported by theS-CSCF in a pre-determined interval of time. For example, an S-CSCFmeasures a peak period volume for each registered UE that it servicesand its overall peak period volume for a particular interval of time.

In step 420, method 400 reports the S-CSCF resource capacity andoptionally each registered UE's resource consumption to a HomeSubscriber Server (HSS). For example, the method may report the measuredinformation to the HSS on an hourly basis.

In step 430, method 400 determines whether or not the peak period volumeexceeds or reaches an on-set threshold. For example, each S-CSCF serveris provided with an on-set threshold. If the on-set threshold is reachedor exceeded, then the method proceeds to step 440. Otherwise, the methodproceeds to step 410.

In step 440, method 400 selects one or more registered UEs whosecumulative peak period volume is larger than or equal to the volume oftraffic in excess of the on-set threshold. For example, the method mayrandomly select a list of candidate UEs. The method may then sum thepeak period volumes of the selected UEs. If the sum of the peak periodvolumes of selected UEs is less than the volume of traffic in excess ofthe on-set threshold, then the method adds more candidate UEs. Theprocess continues until the sum is greater than or equal to the trafficin excess of the on-set threshold.

Alternatively, in step 440, method 400 may select one or more registeredUEs whose cumulative peak period volume is larger than or equal to thevolume of traffic in excess of the off-set threshold. This will likelyredirect more UEs from the current overloaded S-CSCF, thereby reducingthe need of having to redirect additional UEs from the current S-CSCF.

It should be noted that various alternative UE selection methods canalso be employed. For example, one alternative method may rank order theUEs based on their peak period volume and then selecting the xth highestUEs such that the cumulative peak period is equal to or larger than theexcess traffic. Another alternative method may rank order the UEs basedon historical trending of UE resource consumption and then selecting thexth highest UEs such that the cumulative peak period is equal to orlarger than the excess traffic, etc.

In step 450, method 400 sends a request to the HSS, wherein the requestis to re-register the one of more selected UEs on one or more otherS-CSCFs. For example, the method sends a request to move a selected listof registered UEs and each registered UE's resource consumption to otherdevices or servers providing the S-CSCF functionality.

In optional step 460, method 400 may notify the HSS immediately, when aselected UE is idle, or after a preselected time period as discussedabove. For example, the method may have requested to move a first UE toanother S-CSCF. However, the UE may have had one or more active sessionswhile the request was sent. In response, the HSS may have requested tobe notified when the UE has no active sessions, i.e., when the UE isidle. Method 400 then ends in step 470 or returns to step 410.

It should be noted that although not specifically specified, one or moresteps of methods 300 and 400 may include a storing, displaying and/oroutputting step as required for a particular application. In otherwords, any data, records, fields, and/or intermediate results discussedin the methods 300 and 400 can be stored, displayed and/or outputted toanother device as required for a particular application. Furthermore,steps or blocks in FIG. 3 or FIG. 4 that recite a determining operation,or involve a decision, do not necessarily require that both branches ofthe determining operation be practiced. In other words, one of thebranches of the determining operation can be deemed as an optional step.

FIG. 5 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 5, the system 500 comprises a processor element 502(e.g., a CPU), a memory 504, e.g., random access memory (RAM) and/orread only memory (ROM), a module 505 for providing centralizedsubscriber load distribution (e.g., implementing method 300 or method400 as discussed above), and various input/output devices 506 (e.g.,storage devices, including but not limited to, a tape drive, a floppydrive, a hard disk drive or a compact disk drive, a receiver, atransmitter, a speaker, a display, a speech synthesizer, an output port,and a user input device (such as a keyboard, a keypad, a mouse, and thelike)).

It should be noted that the present invention can be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a general purposecomputer or any other hardware equivalents. In one embodiment, thepresent module or process 505 for providing centralized subscriber loaddistribution can be loaded into memory 504 and executed by processor 502to implement the functions as discussed above. As such, the presentmethod 505 for providing centralized subscriber load distribution(including associated data structures) of the present invention can bestored on a computer readable medium or carrier, e.g., RAM memory,magnetic or optical drive or diskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. An apparatus, comprising: a processor; and acomputer-readable medium storing a plurality of instructions which, whenexecuted by the processor, cause the processor to perform operations,the operations comprising: receiving capacity data and user equipmentresource consumption data from a plurality of devices that process callcontrol signaling messages within a communication network; receiving afirst request from one of the plurality of devices to re-register a userequipment that was previously registered with the one of the pluralityof devices; selecting an available device from the plurality of devices;and re-registering the user equipment on the available device.
 2. Theapparatus of claim 1, wherein the selecting selects the available devicewhen a peak period volume of the available device plus a peak periodvolume of the user equipment is less than an off-set threshold of theavailable device.
 3. The apparatus of claim 1, the operations furthercomprising: sending a second request for a notification to the one ofthe plurality of devices that sent the first request, where thenotification indicates when the user equipment is idle.
 4. The apparatusof claim 1, wherein the user equipment is re-registered after allestablished sessions on the user equipment are terminated.
 5. Theapparatus of claim 1, wherein the user equipment is re-registeredimmediately after the available device is selected.
 6. The apparatus ofclaim 1, wherein the user equipment is re-registered after a preselectedtime period.
 7. The apparatus of claim 2, wherein each of the pluralityof devices performs a serving-call session control function.
 8. Theapparatus of claim 3, the operations further comprising: receiving thenotification from the one of the plurality of devices that sent thefirst request when the user equipment is idle.
 9. A non-transitorycomputer-readable storage medium storing a plurality of instructionswhich, when executed by a processor, cause the processor to performoperations, the operations comprising: measuring a resource capacity ofa device that processes call control signaling messages within acommunication network; measuring a peak period volume for each of aplurality of registered user equipment that is registered with thedevice; determining whether a peak period volume of the device reachesan on-set threshold of the device; selecting a registered user equipmentof the plurality of registered user equipment when the on-set thresholdof the device is reached, where a sum of the peak period volumes of theregistered user equipment of the plurality of registered user equipmentis larger than or equal to a volume of traffic that is in excess of theon-set threshold; and sending a request for the registered userequipment of the plurality of registered user equipment to bere-registered to another device.
 10. The non-transitorycomputer-readable storage medium of claim 9, further comprising:reporting the resource capacity of the device to a home subscriberserver.
 11. The non-transitory tangible computer-readable storage mediumof claim 9, wherein the selecting the registered user equipment of theplurality of registered user equipment is performed in accordance with arandom selection algorithm.
 12. The non-transitory tangiblecomputer-readable storage medium of claim 10, wherein the request issent to the home subscriber server.
 13. The non-transitory tangiblecomputer-readable storage medium of claim 9, wherein the request is sentto a load managing server.
 14. The non-transitory tangiblecomputer-readable storage medium of claim 10, further comprising:notifying after a time period, the home subscriber server when one ofthe plurality of registered user equipment is idle.
 15. An apparatus,comprising: a processor; and a computer-readable medium storing aplurality of instructions which, when executed by the processor, causethe processor to perform operations, the operations comprising:measuring a resource capacity of a device that processes call controlsignaling messages within a communication network; measuring a peakperiod volume for each of a plurality of registered user equipment thatis registered with the device; determining whether a peak period volumeof the device reaches an on-set threshold of the device; selecting aregistered user equipment of the plurality of registered user equipmentwhen the on-set threshold of the device is reached, where a sum of thepeak period volumes of the registered user equipment of the plurality ofregistered user equipment is larger than or equal to a volume of trafficthat is in excess of the on-set threshold; and sending a request for theregistered user equipment of the plurality of registered user equipmentto be re-registered to another device.
 16. The apparatus of claim 15,further comprising: reporting the resource capacity of the device to ahome subscriber server.
 17. The apparatus of claim 15, wherein theselecting the registered user equipment of the plurality of registereduser equipment is performed in accordance with a random selectionalgorithm.
 18. The apparatus of claim 16, wherein the request is sent tothe home subscriber server.
 19. The apparatus of claim 15, wherein therequest is sent to a load managing server.
 20. The apparatus of claim16, further comprising: notifying after a time period, the homesubscriber server when one of the plurality of registered user equipmentis idle.